This invention relates generally to endoscopes and, more particularly, to improvements in apparatus for cleaning and sterilizing a guide tube for a forceps-control member operating wire in an endoscope.
It is well known that when a forceps-control member, for example a so-called forceps-riser, is raised and allowed to be lowered or collapsed through the manipulation of an operating wire to perform various operations in connection with a biopsy, i.e., an inspection of living tissue, fluid secreted from the body, such as gastric juice or mucus and blood, often invades the interior of the wire guide tube through its forward opening.
Thus, generally, biopsy operations wherein a sample of living tissue is removed from the tissue of a body cavity, have recently been accomplished using endoscopes which are adapted to perform such operations in addition to the usual observations and diagnosis generally performed during inspections using endoscopes. Accordingly, modern endoscopes are generally provided with a picker, such as forceps, for partially removing living tissue from the wall of a body cavity or organ, a forceps-control member, such as a riser mounted in a forward region of the portion of the endoscope which is introduced into the body cavity for controlling the orientation of the picker, an operating wire connected to the forceps-control member for movably driving the same, a guide tube through which the operating wire passes to guide the latter to a manipulator unit, and a control mechanism connected to an end of the operating wire mounted on or in the manipulator unit which is manually operated to pull or slacken the operating wire to thereby raise the forceps-control member or allow the same to collapse.
However, as mentioned above, it is inevitable that fluids secreted from the body, blood or the like, will enter or invade the interior of the guide tube through the small gap defined between the operating wire and the wire guide tube under the effect of pressure present within the body cavity created during the manipulation of the instrument to direct the picker, e.g. the forceps, onto the precise desired location in the body cavity. In particular, the secreting fluid, blood or the like, will invade the interior of the guide tube along the plies of the stranded operating wire as the latter is pulled.
In an attempt to overcome this problem, an arrangement is disclosed in Japanese Utility Model Laid-Open Application No. 1976-38986 wherein the operating wire guide tube is provided along its inner periphery at the front end thereof with a suitable sealing member by which the fine gap present between the guide tube and the operating wire is sealed. However, it has been found that the sealing of the gap using such an arrangement in practice results in an increase in the load exerted on the operating wire during its movement resulting in an obstruction in the smooth manipulation of the wire and consequently adversely affecting the maneuverability of the endoscope as a whole. It has also been found that such gap sealing arrangement cannot completely seal the interior of the wire guide tube from the secreting fluid, blood or the like, along the plies of the stranded operating wire. More disadvantageously, use of the gap sealing arrangement disclosed in the above-mentioned Japanese application has shown that the sealing member prevents cleaning and sterilizing liquid for the secreting fluid, blood or the like from flowing smoothly within the wire guide tube thereby rendering an efficient cleaning and sterilization thereof impossible.
The introduction or invasion of secreting fluid, blood or the like along the operating wire into the wire guide tube which occurs when the picker, such as forceps, is manipulated is extremely undesirable for the following reasons. Thus, such fluid will cause the wire to rust and, additionally, will cause a clogging of the guide tube when the fluid dries thereby preventing the operating wire extending therethrough from being smoothly moved. In extreme cases, invasion of secreted fluids, blood and the like into the guide tube will continue into the manipulator unit whereupon both the interior as well as the exterior of the manipulator unit will become contaminated by the fluid causing subsequent manipulation of the unit to become more difficult. The invasion of such body fluids is also undesirable from the medical viewpoint in that after the endoscope is used with a patient who is syphilitic, Autrali antigen positive or the like, use of the same endoscope in another patent may cause that disease to be transmitted to the new patient. In order to avoid this danger, both the exterior and the interior of the endoscope must be cleaned and sterilized prior to every use or, at the least, quite often. Such cleaning and sterilization is more easily achieved with higher efficiencies when the quantity of secreting body fluid, blood or the like which invades the guide tube can be reduced. Accordingly, it is desirable to maintain the quantity of such secreting fluid, blood or the like which invades the guide tube at a minimum.
In order to most efficiently eliminate the invasion of fluids into the guide tube as described above, it might be proposed to reduce the inner diameter of the guide tube relative to the diameter of the operating wire to the extent possible so long as the load resisting the movement of the operating wire is not thereby increased to an unacceptable level. However, it must be kept in mind that the reduction of the inner diameter of the guide tube relative to the diameter of the operating wire will disadvantageously obstruct a smooth flow of cleaning and sterilizing liquid through the guide tube. In this connection, in order to prevent the secreting fluid, blood or the like which has invaded the guide tube from further movement into the manipulator unit from which it can then leak to the exterior as well as to facilitate the discharge of the fluid which has invaded into the endoscope during the rinsing operation, it has been proposed to provide a hollow room within the manipulator unit, which room is provided with a piston-like slidable member for preventing leakage of the liquid, the end of the operating wire being operatively associated with the slidable member. An opening is also provided in the hollow room which communicates with the exterior of the manipulator unit for a rinsing operation. This arrangement inhibits the flow of fluid which has invaded the guide tube from further flow into the hollow room and subsequently leaking therefrom to the exterior of the manipulator unit and also allows the fluid remaining in the hollow room to be discharged through the opening to the exterior for rinsing. Moreover, rinsing liquid can be injected through the opening into the hollow room and the guide tube to thereby achieve a desired rinsing or cleaning effect.
However, this arrangement also presents problems in that movement of the operating wire for effecting the raising or collapsing of the forceps-control member, e.g. the forceps-riser, which is connected to the wire and, therefore, the orientation of the picker, e.g. the forceps, necessarily relies upon the reciprocating motion of the piston-like member for prevention of leakage. However, each stroke of the piston-like member results in the secreting fluid, blood or the like being sucked from or forced into the guide tube through the opening or gap at the forward end of the guide tube resulting in the invasion of the secreting fluid, blood or the like being unexpectedly promoted by the arrangement.
It is also well known to provide a channel in communication with the hollow room through control means, such as a communication control valve, to supply water or air thereto primarily for cleaning a location to be inspected. Thus, this separate channel may be utilized for a desired rinsing or cleaning operation. However, such a water or air supply channel usually has opposed ends which are opened so that the small gap defined between the guide tube and the operating wire extending therethrough cannot produce a sufficiently high resistance within the tube to increase the inner pressure during injection of the rinsing liquid so as to maintain a smooth flow of the rinsing liquid through the gap between the wire and the guide tube. Thus, an adequate rinsing effect cannot be expected using this arrangement.
With respect to the effect of variations in the inner diameter of the wire guide tube on the flow rate of manually injected rinsing water, tests have been conducted the results of which are illustrated in FIG. 4 which graphically illustrates the flow rate of cleaning water versus the inner diameter of the guide tube for the operating wire. In this experiment, the operating wire constituted by a stranded wire having an outer diameter of 0.63 mm was used. The inner diameter of the wire guide tube was varied from 0.8 mm through 0.85 mm, 0.9 mm, 0.95 mm to 1.05 mm. The results of the experiment are set forth in the following table:
______________________________________ Inner diameter of guide tube Injected flow rate/min. ______________________________________ 0.8 mm 12 c.c. 0.85 mm 19 c.c. 0.9 mm 26 c.c. 0.95 mm 30 c.c. 1.05 mm 40 c.c. ______________________________________
In the experiment, the rinsing water was injected by an injection pump under a manual pressure. As the results shown in FIG. 4 and the above table indicate, although it is preferable to minimize the cross-sectional area of passage defined between the outer surface of the operating wire and the inner surface of the wire guide tube in order to suppress the quantity of the secreting fluid, blood or the like which may invade the wire guide tube through the end thereof, an excessive reduction of this sectional passage area at the same time will constrict the sectional passage area through which the injected rinsing water passes thereby making the desired injection difficult. Accordingly, it will be understood from these test results that are pointed out above the passage resistance within the guide tube would not be sufficiently high to obtain the desired rinsing effect even when the wire guide tube communicates with the separate water or air supply channel, which usually has a relatively large diameter, so as to rinse the interior of the wire guide tube by injecting rinsing water through that separate channel, since the latter is usually not a closed tube but, rather, generally comprises a tube having open opposite ends. The results of the experiment indicate that the inner diameter of the guide tube should preferably be on the order of about 0.8 mm or greater when a stranded wire having an outer diameter of 0.63 mm is used in order to obtain a smooth flow of water through the wire guide tube under manual pressure. In this case, the sectional passage area will be on the order of about 0.17 mm.sup.2. The experiment indicates that when the sectional passage area is less than about 0.17 mm.sup.2, the force required for injecting rinsing water becomes too large to allow for the desired maneuverability.
Thus, as indicated above, in order to minimize the invasion of secreting fluid, blood or the like into the wire guide tube through the fine gap formed at its forward end, the sectional passage area must be as small as possible, such reduction in the sectional area being limited to a reasonable degree by considerations of maneuverability during rinsing or cleaning operations. In practice, the inner pressure within the body cavity and the capillary phenomenon which occurs along the plies of the stranded operating wire make it difficult to entirely suppress invasion of the secreting fluid, blood or the like into the guide tube. Moreover, it is extremely important to avoid the phenomenon wherein the necessary manipulation for controlling the orientation of the picker, such as forceps, produces a negative pressure within the guide tube through motion of the piston-like member as discussed above.